Fix a regression in the previous release that broke switching to neighboring windows in the Grid layout when there are less than four windows

Fixes #2377

docs/changelog.rst

@@ -46,6 +46,9 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - macOS: When switching input method while a pending multi-key input is in
   progress, clear the pending input (:iss:`2358`)
 
+- Fix a regression in the previous release that broke switching to neighboring windows
+  in the Grid layout when there are less than four windows (:iss:`2377`)
+
 
 0.16.0 [2020-01-28]
 --------------------

kitty/layout.py

@@ -839,6 +839,7 @@ class Grid(Layout):
     def neighbors_for_window(self, window, windows):
         n = len(windows)
         if n < 4:
+            self.num_full_size_windows = 1
             return Tall.neighbors_for_window(self, window, windows)
         ncols, nrows, special_rows, special_col = calc_grid_size(n)
         blank_row = [None for i in range(ncols)]